Through this test I learned that 255-thread/in. mesh is not nearly as friendly a mesh to halftones as a 230- thread/in. mesh and that 47- and 55-line/in. halftones work very well on all the necessary meshes for the shop in which I tested them. The thing to remember is that this may not apply to every shop because the variables are different from facility to facility. Your shop has different mesh, films, screen tension, exposure times, emulsion thickness, and press variables. All of these elements can expose the need for a different halftone resolution that will create the best dots just for you.

The printers out there who have experienced the fantastic results that only index separations can bring will appreciate the index testing meth-od for determining the ideal resolution of the dots they can hold. For this test, it’s better to import the gradient strips into CorelDRAW or Adobe Illustrator so that the different resolutions will keep the square dots nice and sharp (Figure 4). Go through your favorite meshes with the same file and you’ll quickly see which resolutions you can hold with this method. You’ll more than likely be surprised at how high a resolution you can maintain. Several printers that I tested could easily hold index frequencies above 200 lines/in. and get some great prints that blend so well the naked eye can’t see any dots at all. This simple test may make you rethink the index method. If you can hold a finer dot for better detail than a traditional halftone and you have at least an eightcolor press, why not? The key is in conducting the test and seeing what really works in a production setting and then pushing it a little to get the best quality possible.

Become a dot detective

The best dot for your shop is only a simple test or two away. Once you’ve finished the test, you can really get a handle on standardizing mesh-to-resolution rates, eliminate moiré, achieve better detail, and improve overall quality control. Testing this way with the index method is an amazing process that can completely change the mindset of experienced printers when they see what kind of detail is possible without the edge-quality loss shown by conventional halftones. Use both tests to quickly find the best dot for all of your work now!

Thomas Trimingham is an award-winning art director, illustrator, and separator who has more than 16 years of experience in the screen-printing industry. He can be reached at ttrimingham@yahoo.com.